Appetite, 1992, 19, 61-68

Commentary Where Should Human Eating be Studied and What Should be Measured? HARRY

R. KISSILEFF

Departments of Psychiatry and Medicine, Columbia University, College of Physicians and Surgeons, and New York Obesity Research Center St LukeS/Roosevelt Hospital Center New York, NY, U.S.A.

Meiselman’s (1992) proposal for redirection of research on human eating behavior towards eating in real settings is misdirected, because it does not take into consideration the questions being addressed by laboratory studies. In fact many of the studies for which he has called have in fact been done and will be cited. There is no compelling scientific or strategic reason that investigators who are making good progress on the problem of what controls the amount eaten should be exhorted to examine what controls the place or time of eating or what is selected for eating. They are different problems which require different methodology. The field is large enough for both kinds of studies and there is no reason to berate investigators as Meiselman does for not investigating the problem he happens to be studying. INTRODUCTION

Meiselman (1992) claims that investigators who study human eating behavior in laboratories are working in an unrealistic environment. Because this claim is also frequently made by those who have not actually studied human eating in the laboratory, a group which ironically includes many who study the neurobiology of food intake control in rats living in laboratories, it is important to justify the laboratory as an appropriate place for such studies. The reason Meiselman declaims laboratory studies is that they do not answer the major questions he asks at the outset of his paper (Meiselman, 1992): “What controls when we eat, what we eat, and why we eat?’ The answers to these questions require a different methodology from the question “what controls how much people eat and when they stop eating?“. The questions Meiselman asks do not particularly lend themselves to the laboratory, so it is not surprising that he is critical of laboratory investigations. However, because Meiselman moves beyond methodological concerns to conclude that laboratory research is unrealistic, it is important to point out what laboratory research in fact provides so that we will not reject it for the wrong reason, i.e. because it fails to answer questions which it has not been designed to address. I shall divide this critique into two sections. The first will deal in general with Meiselman’s claim that the laboratory is an artificial place to study eating in humans Addresscorrespondenceto: Harry R. Kissileff,St Luke’sHospital,114thSt & AmsterdamAve.,New York, NY 10025, U.S.A. 01954663/92/040061+08

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and that therefore more research should be done in “real” situations. The second part will deal with several specific issues growing out of the generality.

GENERALCONSIDERATIONS One retort which comes immediately to mind about Meiselman’s claim is whether the claim itself is artificial. When one refers to environments in which eating takes place, are the terms “real” and “artificial” scientifically definable end points along a continuum, like black and white, or simply arbitrary designations? Humans eat in almost every conceivable situation in which they find themselves, from busy subways, to beds, and in every conceivable grouping, from eating alone in a hospital room, whether sick or well, to eating in huge groups, either in banquets or on battlefields. To claim that the US army cafeteria at Natick, or elsewhere is a more realistic eating situation than the laboratory, implies that there is some yardstick by which to classify environments, yet Meiselman gives us no such criteria for this classification. What then is the relationship of the research enterprise to the setting in which the research takes place? The issue should not be the percentage of the research (in units of subjects studied, papers published or dollars spent) done in a particular environment, but what percentage of the behavior takes place in that environment. Since Meiselman offers no scientific procedures for determining what a “real environment” is for eating, we offer two possible solutions: either (1) a cafeteria or (2) a place where most of a person’s eating occurs. According to the latter criterion, the “real/artificial” dichotomy turns on the variable of frequency of eating in various settings (i.e. alone, with people, in cafeteria, or in one’s dining room). A better strategy than definition by fiat would be to determine what percentage of human eating episodes occur in various environments. Then, if we are interested in what controls eating in the environment where most of the eating takes place, we should conduct studies to determine whether the controls are different in that place than in others. An attempt by the present author to obtain such data turned up only a few published reports (Davis et al., 1988; Peterkin et al., 1987). Two types of national surveys in the US (USDA, and NHANES), in fact, collect data that could be used to determine the frequency of eating in various environments and neither has apparently been sufficiently tapped to extract the data we would want. Studies on a smaller scale [n=82 in (de Castro, 1990) vs 4400 (Davis et al., 1988)], may be too restricted a sample to draw general conclusions. Nevertheless, based on the existing data in middle-aged people (Peterkin et al., 1987) it appears that at least one-third of eating events takes place while people are eating alone, one-third takes place in restaurants, and one-third takes place at work. While the last two were mutually exclusive, the first was not, and therefore the critical data on how the number of people in an eating episode interacts with the environment still needs exploration. Living arrangements play a critical role in determining whether meals are eaten alone or with others. In adults aged 55-98, living alone, 85% of meals were eaten alone, while in adults living with spouses only 20% of meals were eaten alone (Davis et al., 1988). However, even though the data are available, the direct effects of living alone, and eating alone, on intake were not analysed (Murphy et al., 1990).

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In other words, the real question regarding the issues Meiselman wants us to address is whether the controls of eating differ from one environment to another. Eating is, after all, a behavioral act which has a biological basis, as reviewed almost ad nauseum [e.g. @tricker, 1990; Novin er al., 1976)]. If Meiselman is proposing that this basic tenet be dismissed, then there is no basis for continuing the dialogue. Proposing that the physiological controls of eating are different in a cafeteria than in a laboratory is like proposing that any other physiological function has different controls in different places. For example is control of cardiovascular function different on the football field than in the doctor’s office? To the extent that a competitive sport may induce more cardiovascular stress than the examining room, an assertion of dubious veracity, the controls might differ. It seems more likely that the controls are the same in the two settings, but that the values of their outputs (e.g. blood pressure) differ from place to place depending on the situation to which the individuals must adapt. Likewise the amount consumed might vary depending upon whether a person was in a sports stadium, a laboratory or a cafeteria, but there is no reason to believe that there would be an interaction between the input-output relationships (Booth, 1989a), such as physical qualities of the foods or their postingestional effects, and how much was consumed and the environment in which the eating took place. If such interactions were observed, it would indeed be worthy of full scientific investigation of their bases. What evidence is there that the controls of eating about which we know (e.g., the effects of physical properties, postingestive effects of foods, moods and feelings which are related to being alone or being with others, etc.) differ from place to place? Will a certain energy load be more or less effective in suppressing intake in a cafeteria than in a laboratory, or will there be no difference? Without an answer to this basic question, it is fruitless to tout one environment for studying eating over another by mere labeling of the environment in which the study is conducted with an unscientific designation (i.e. “real life”).

SPECIFIC kXJES

With regard to the specific issues, I will address six: (1) the option not to eat and the effect of scheduling eating; (2) the relationship between amounts eaten in and out of laboratories; (3) the influence of the experimenter’s choice of eating place, instructions, and the design of studies; (4) the choice of food for laboratory eating studies; (5) the role of economic and social conditions in the control of eating; (6) the study of abnormal vs. normal eating.

COERCION AND SCHEDULED EATING

Subjects eating in laboratories have the same options of rejecting food as people eating in cafeterias. Human ethics committees will not permit coercion, however subtle, and unless subjects are paid by the amount eaten, which might make an interesting study in itself, there is no reason to believe that they must eat. In our own studies we have occasionally found that people refuse to eat. Meiselman has not demonstrated that subjects eat in cafeterias because they are hungry rather than because their eating has been scheduled. If one’s goal is understanding what controls

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amount of energy consumed, which is the variable most directly connected with health and body weight, it is logically more efficient to focus on the controls of the termination of eating, once it has begun for whatever reason, than on what starts it, where it takes place, or what food is selected.

THE RELATIONSHIPBETWEEN AMOUNTS EATEN IN LABORATORIESAND OUTSDE LABORATORIES

It is extremely difficult to obtain an unconfounded measure of the relationship between amounts eaten in and out of laboratories. The problem is measurement outside the laboratory. There are three possible ways to do it. One is to observe the subjects, which may modify intake if they are aware of the observer. The second is to have them recall intake. However, subjects tend to under-report intakes in general (National Research Council, 1989). Furthermore, it has been found that subjects who eat less tend to over-report, while those who eat more under-report, even though the correlation between reported and measured intake was high (0.96) (Stunkard, 1981). For patients with bulimia nervosa, intake reports were exaggerated, rather than reduced, when the actual intakes measured in the laboratory were large (Hadigan et al., 1992). Nevertheless, there was a significant correlation (r=0.59, p-c O-05)between the amount eaten in the laboratory and the amount reported to a skilled dietitian, eaten outside the laboratory, at least for patients with bulimia nervosa (Walsh et al., 1989). Finally self-measurement of intake can be used, but the act of measuring, like keeping a diary, may result in reduced intake, especially in those who may be self-conscious about overeating. Unobtrusive measurement in both places would appear to be the method of choice, but this measurement has apparently not been undertaken.

THE INFLUENCE OF THE EXPERIMENTER’SCHOICE OF EATING PLACE, INSTRUCTIONS, AND THE DESIGN OF STUDIFS

It is not clear to what Meiselman (1992) is referring when he states that “from laboratory studies we develop hypotheses and models about what variables control laboratory eating”. Were he to cite a specific control which could be demonstrated to operate only in the laboratory we would address this assertion. It is usually the opposite sequence; we develop a hypothesis, which then requires a laboratory for testing. As far as the instructions are concerned, it is clear that subjects are sensitive to the demands placed on them, but the effects of these demands appear to vary with the type of food eaten. With ice cream as the test food, intakes were similar, no matter whether the instructions were to merely taste (177 g, Herman & Mack, 1975), eat as a normal meal (165 g), or eat as much as you can (207 g) (LaChaussCe et al., 1992). When the meal was macaroni and beef, the instruction effect was much larger [difference of 204 g (p-cO.05)between instructions to eat without bingeing or restricting and eat as much as you can (Hadigan et al., 1992)]. Furthermore, the possibility that these instructions interact with subjects’ responses to preloads and hence the mechanism that controls eating is certainly an issue that needs more

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exploration. We agree with Meisehnan and Booth (Booth, 1989b) before him that the effects of many foods, either one at a time or in groups, must be examined.

THE CHOICE OF FOOD FOR LABORATORYEATING STUDIED In response to the question “How many of our studies involve real meals or diets constituted as the subjects would choose?’ it is ironic that the choice of macaroni and beef as the food for test meals to study in our laboratory was based on survey data, collected by Meisehnan himself (Meiselman et al., 1974) which showed that this meal was highly liked, by most subjects. None of these laboratory studies, which used “real foods” (Kissileff, 1984; Muurahainen et al., 1988; Muurahainen et al., 1991) is cited. Many investigators ourselves included (Kissileff et al., 1986; Walsh et al., 1989) have studied meals containing multiple items, e.g. (Hill & Blundell, 1986; Rodin, 1990; Rolls et al., 1988) in an effort to provide just what Meiselman decries. A more important issue which does need to be addressed seriously is whether single or multiple item meals are better dependent variables. In patients with bulimia, but not in normal controls, intakes of single and multiple item meals were correlated (LaChaussCe et al., 1992). This finding raises the questions, will a manipulation such as a preload, instruction, or infusion give more reliable data when multiple items are used, and can the controls of food choice be disconfounded from controls on amount consumed when multiple items are present. It would appear that methodological studies are needed to determine the best type of meal for studies of the effects of independent variables on the amount consumed.

THE ROLE OF ECONOMIC AND Socm~ CONDITIONS IN THE CONTROL OF EATING The role of social and economic factors are important issues in the control of food intake, but not questions suited to laboratory investigation. Nor is it clear, whether, or how, these factors would interact with factors that control intake. If the two types of factors are simply additive, there is no great advantage to one or another social or economic situation. On the other hand if interactions exist, it would be important to explore their mechanism. The study of such interactions is a major unexplored area in human ingestive behavior.

ABNORMAL vs. NORMAL EATING

There are a number of strategies for studying abnormal eating. Although Teitelbaum (Teitelbaum, 1967) exhorted his students that when confronted with the complexity of neural controts of behavior, study of the simplified abnormal would reveal the normal; in human eating behavior, my experience has been the reverse. In order to understand a disturbance in eating behavior, it is necessary to have a test of a normal response to a manipulation. One of the best strategies would appear to be studying them both under similar conditions, which can best be done by arranging

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the conditions so that intake can be measured from the individual eater undisturbed by other factors. The laboratory provides an ideal environment for such studies. We (Kissileff & Kral, 1986; Walsh et al., 1989; LaChausste et al., 1992) and others (Rolls, 1991; Yanovski et al., 1992) have compared individuals who do not report eating disturbances with those who do. In attempting to explain the abnormalities in eating we have observed, we are frequently confronted with an absence of demonstrations of normal controls for which we can probe abnormal eaters. It seems therefore that what is needed is a combination of research into the mechanisms of normal control combined with how these mechanisms are disturbed during abnormal eating. Indeed the categories of normal and abnormal eating themselves have yet to be scientifically defined. Both DMSIII and the proposed DSMIV include such vague terminology as “binge”-“. . . an amount of food that is definitely larger than most people would eat. . .“. It would be difficult to imagine a less precise formulation. Such vagueness should be replaced by norms of what people of various ages, sexes, heights, weights, etc. eat, and criteria for what percentage of the tail of the distribution should be considered “abnormal”. The data needed to make these determinations are available from national surveys [NCHS (National Center for Health Statistics), 1979; U.S. Dept of Agriculture, 19841 at least in the USA, but they are rarely, if ever, cited in the literature on the control of food intake.

SUMMARY In summary, Meiselman has raised a number of important issues about how human eating behavior is, can and should be studied. The challenge for the future is to look beyond the notion that laboratory eating is unrealistic and that the cafeteria is a model for the real world, to hypothesis testing about the factors that control food intake. By focusing so intently on the place in which the studies are done, Meiselman has overlooked one of the critical questions which needs to be addressed. The study of eating behavior involves the study of factors which control amount consumed, selection of foods to consume, and selection of place to eat. The control of food intake, i.e. amount consumed once a choice has been made, is best studied in the laboratory where it can be measured and the factors that control it can be manipulated. The question of choice of items and place of eating is a separate issue which is perhaps better studied by probing the reasons that people make choices in general, irrespective of controls of food intake. It would be helpful in evaluating Dr Meiselman’s claims about relative strengths of laboratories and cafeterias for him to demonstrate that subjects prefer to eat in the cafeteria rather than alone and under what conditions, that they prefer items in the cafeteria to those they could prepare themselves, and that they choose the time to eat rather than have it scheduled. What is the role of the subject’s choice in each of these decisions on the subject’s intake? If it matters, then we may have another go at this in a few years. If not, we should choose the most efficient paradigm and continue to explore what factors induce some people to eat more than they expend and what can be done to help them bring their intakes and expenditures into equilibrium, thereby promoting better health. Further studies of the USDA and NIH data collected on large groups of people may

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provide insights into some of these issues, in particulr insights into the role of socialization, setting, and life-style on the control of amount eaten.

REFERENCES

Booth, D. A. (1989a) Mood- and nutrient-conditioned appetites--Cultural and physiological bases for eating disorders. Annals of the New York Academy of Sciences, 575, 122-135. Booth, D. A. (1989b) The effect of dietary starches and sugars on satiety and on mental state and performance. In: J. Dobbing, (Ed.), Dietary starches and sugars in man a comparison. Pp. 225-249. New York: Springer-Verlag. Davis, M. A., Murphy, S. P. & Neuhaus, J. M. (1988) Living arrangements and eating behaviors of older adults in the United States. Journal of Gerontology: Social Sciences, 43, S96-S98.

de Castro, J. M. (1990) Social facilitation of duration and size but not rate of spontaneous meal intake of humans. Physiology and Behauior, 47, 1129-l 135. Hadigan, C. M., Walsh, B. T., Kissileff, H. R., LaChauss&, J. L. & Devlin, M. J. (1992) Behavioral assessment of satiety in bulimia nervosa. Appetite, 19, 233-242. Herman, C. P. & Mack, D. (1975) Restrained and unrestrained eating. Journal of Personality, 43, 647-660.

Hill, A. J. & Blundell, J. E. (1986) Model system for investigating the actions of anorectic drugs: Effect of D-fenfluramine on food intake, nutrient selection, food preferences, meal patterns, hunger and satiety in healthy human subjects. In Advances in the biosciences. Oxford: Pergamon Press. Kissileff, H., Walsh, T., Kral, J. & Cassidy, S. (1986) Laboratory studies of eating behavior in women with bulimia. Physiology and Behavior, 38, 563-570. Kissileff, H. R. (1984) Satiating efficiency and a strategy for conducting food loading experiments. Neuroscience & Biobehavioral Reviews, 8, 129-135. Kissileff, H. R. & Kral, J. G. (1986) Abnormal eating behavior in obese men and women. In 5th International Congress on Obesity, Jerusalem, Israel, 14 September 1986. LaChausske, J. L., Kissileff, H. R., Walsh, B. T. & Hadigan, C. M. (1992) The single item meal as a measure of binge-eating behavior in patients with bulimia nervosa. Physiology and Behavior, 51, 593-600.

Meiselman, H. L. (1992) Methodology

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Meiselman, H. L., Waterman, D. & Symington, L. E. (1974) Natick, Dec.: U.S. Army Natick Laboratories Technical Murphy, S. P., Davis, M. A., Neuhaus, J. M. & Lein, D. dietary adequacy and energy intake of older Americans.

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Muurahainen, N. E., Kissileff, H. R., De Rogatis, A. J. & Pi-Sunyer, F. X. (1988) Effects of cholecystokinin-octapeptide (CCK-8) on food intake and gastric emptying in man. Physiology and Behavior, 44, 645-649.

Muurhainen, N. E., Kissileff, H. R., Lachausske, J. & Pi-Sunyer, F. X. (1991) Effect of a soup preload on reduction of food intake by cholecystokinin in humans. American Journal of Physiology, 260, R672-R680. National Research Council (1989) Recommended Dietary Allowances 10th Editition, Pp. l-284. National Academy Press, Washington, DC: National Research Council (U.S.) Subcommittee on the Tenth Edition of RDA’s Food and Nutrition Board, Commission of Life Sciences, National Academy Press, Washington, D.C. NCHS (National Center for Health Statistics), (1979) Dietary Intake Source Data, Hyattsville, MD: DHEW Publ. No. 79-1221, NCHS. Novin, D., Wyrwicka, W. & Bray, G. A. (1976) Hunger, basic mechanisms and clinical implications, New York: Raven Press. Peterkin, B. B., Rizek, R. L., Posati, L. P. & Harris, S. S. (1987) When, where, with whom and what older Americans eat. Gerodontics, 3, 14-19.

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Rodin, J. (1990) Comparative effects of fructose, aspartame, glucose, and water preloads on calorie and macronutrient intake. American Journal of Clinical Nutrition, 51, 428-435. Rolls, B. J. (1991) Effects of intense sweeteners on hunger, food intake, and body weight: a review. American Journal of Clinical Nutrition, 53, 872-878. Rolls, B. J., Hetherington, M. & Burley, V. J. (1988) The specificity of satiety: The influence of foods of different macronutrient content on the development of satiety. Physiology and Behavior, 43, 145-153.

Stricker, E. M. (1990) Handbook of Behavioral Neurobiology, Volume 10, Neurobiology of Food and Fluid Intake, New York, NY: Plenum Publishing Corp. Stunkard, A., J. (1981) “Restrained Eating”: What it is and a new scale to measure it. In: L. A. Cioffi, W. P. T. JTB. VI (Ed.), The body weight regulatory system: Normal and disturbed mechanisms. Pp. 243-251. New York: Raven Press. Teitelbaum, P. (1967) Physiological psychology: fundamental principles, Englewood Cliffs, NJ: Prentice Hall. U.S. Dept. of Agriculture (1984) Food intakes: Individuals in 48 states, year 1977-78. Nationwide food consumptoion survey report No. Z-2, Hyattsville, MD: Nutrition Monitoring Division, Human Nutrition Information Service, USDA. Walsh, B. T., Kissileff, H. R., Cassidy, S. M. & Dantzic, S. (1989) Eating behavior of women with bulimia. Archives of General Psychiatry, 46, 54-58. Walsh, B. T., Kissileff, H. R. & Hadigan, C. M. (1989) Eating behavior in bulimia. Annals of the New York Academy of Sciences, 575, 446-455.

Yanovski, S. Z., Leet, M., Flood, M., Yanovski, J. A., Gold, P. W., Kissileff, H. R. & Walsh, B. T. (1992) Food intake and selection of obese women with and without binge-eating disorder. American Journal of Clinical Nutrition (in press).

Where should human eating be studied and what should be measured?

Meiselman's (1992) proposal for redirection of research on human eating behavior towards eating in real settings is misdirected, because it does not t...
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